Transcript for Controversial Pentagon Contract for Russian Helicopters Under Scrutiny

Meantime, the pentagon under fire tonight for its decision to buy combat helicopters made in russia. Lawmakers on both sides, asking, why not made in america? Here tonight, abc's aditi roy. Reporter: Tonight, new questions arise as to why the pentagon chose to spend more than $1 billion on dozens of russian mi-17 helicopters, to support afghan troops, bypassing u.S. Manufacturers. The defense department signed the deal more than two years ago and pentagon officials defended the move, citing a 2010 top secret study, which they said recommended the russian helicopter as the top choice. But the associated press has obtained excerpts of the study, which said the u.S. Manufactured chinook helicopter was the, quote, most cost effective single platform type fleet for the afghan air force over a 20-year period. E russian deal sparking outrage in congress, as lawmakers pressed officials during defense department budget hearings in april. With all the tens of billions of dollars we put into afghanistan, this is a tough one to justify. Reporter: The defense department says the afghan military already trains and uses the russian chopper, while the u.S. Chinook would require retraining baf gan forces. We are trying to provide them as much capability as possible, so that they can, in fact, take responsibility for security. Reporter: A pentagon spokesman tells abc news the russian helicopter is the only one that could meet our immediate and near-term requirements in afghanistan. The pentagon says it has PURCHASED 63 BRAND NEW MI 17s AT An average cost of $8 million per aircraft. The last shipment is scheduled to be on the ground by september of 2014.

This transcript has been automatically generated and may not be 100% accurate.

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